Adding in a few 503 status codes for common errors in response to this ExpressionEngine bug about errors getting cached by reverse proxies who cache 200 responses: http://expressionengine.com/bug_tracker/bug/17420
diff --git a/index.php b/index.php
index 1712a7d..a378266 100644
--- a/index.php
+++ b/index.php
@@ -218,6 +218,7 @@
 	{
 		if ( ! is_dir(BASEPATH.$application_folder.'/'))
 		{
+			header('HTTP/1.1 503 Service Unavailable.', TRUE, '503');
 			exit('Your application folder path does not appear to be set correctly. Please open the following file and correct this: '.SELF);
 		}
 
@@ -233,6 +234,7 @@
 	{
 		if ( ! is_dir(APPPATH.'views/'))
 		{
+			header('HTTP/1.1 503 Service Unavailable.', TRUE, '503');
 			exit('Your view folder path does not appear to be set correctly. Please open the following file and correct this: '.SELF);
 		}